The invention relates to a hearing aid. Inner-ear hearing aids are introduced deep into the auditory canal so as to be substantially invisible from the outside. The same is true for outer ear hearing aids where the ear mold or ear piece (connected with the apparatus housing via a sound conduction tube) is to be introduced quite deep into the auditory canal. This brings the mouth of the sound conduction line into the zone of the auditory meatus in which secretions called cerumen are deposited. This substance may clog the opening of the sound channel. For this reason so-called cerumen catchers or traps have been provided. These, however, are difficult to keep clean, as in the case of the apparatus of German Utility Model No. 19 51 165, and they generally constitute an undesired enlargement of the housing. In the case of German Offenlegungsschrift No. 28 18 273, the sound exit opening is covered with a rubber cap, which may be formed like a sieve. According to page 4, lines 1 to 5 of this disclosure, the ear mold is always shaped a little bulged, so that the slightly thickened edge of the protective cap can be fixed in a notch already existing or specially created for this purpose. For a still more secure hold of the cap, it may be rubberized internally wholly or partly, so that it sticks. A rubber cap of the kind described has the disadvantage, apart from tearing easily, that after having been fitted over the apparatus part to be introduced into the auditory meatus it applies thereon relatively smoothly, even if its outside is rough. Therefore, the cerumen slides quickly along the protective cap toward the sieve-like openings over the sound channel. Hence the openings become clogged sooner than necessary and accordingly the cap must be replaced more frequently.
One object of the invention is to provide a hearing aid of the initially mentioned kind with a protective device associated with the sound transmission line and effective against secretions of the auditory canal, whereby the cerumen reaches the sieve openings less quickly, so that the protective device requires less frequent replacement or cleaning.